[Pattern of the brain damages and its developmental mechanisms in monozygotic twins]

Neurologic morbidity is observed more frequently in twins than in singletons. Low birthweight and premature birth are observed more frequently in twins but cannot always explain the cause of cerebral palsy, although circumstances related to twinning may cause brain damage. We attempted to select the patients whose brain damages might be caused by circumstances related to twinning and discussed the developmental mechanisms of their brain damages. We divided the cases into 3 groups. One comprised the monozygotic (MZ) twins whose co-twins had died. The second comprised the MZ twins with the complication of the twin-twin transfusion syndrome or discordant twins. The third comprised the MZ twins with concordant co-twins. We postulated that group I and II had complication of the disturbance of fetal circulation, but group III did not. Hydranencephaly (group I) and polymicrogyria (group II) might develop when the disruption occurs at an intermediate stage of morphogenesis (before the 6th month of gestation). In the cases with cerebral infarction (group I), the distribution of the lesions were related to the main vascular territories of the mature form, might be caused by occlusion of blood vessels associated with intrauterine disseminated intravascular coagulation. In the cases of MCE (group I), multiple cavities are present mainly in the white matter, the gray matter having a tendency to be spared. As the distribution of the cavities is not related to the main vascular territories, it was less likely that the lesions was produced by occluded vessels. The death of one fetus might cause severe blood deprivation, leading to hypoxic-ischemic brain insults in the surviving fetus.(ABSTRACT TRUNCATED AT 250 WORDS)